Sasoris high speed almost matches Gaaras speed (if Sasori has his 3rd dupe unlocked) and his HP makes him a good replacement for Gaara on this game mode.

Sasori´s purpose is not to make high damage with his jutsus, but to damage enemies with slip damage, finish off weakened enemies, tank damage (15% damage reduction), running and support BRV and WIS units with his Buddy and Field Skill´s. His jutsu can make up to 7.5K damage to BRV, HRT, SKL and BOD units, while making 11K damage to WIS enemies; and his ultimate can make up to 26K damage to BRV, HRT, SKL and BOD units, while making 39.8K to WIS enemies.

His Sync Skills are also very useful (depending on who you put him with), because it nullifies Switch Seal (if he syncs with BRV and WIS) and nullifies Chakra Seal (if he syncs with long range). Useful against Sasuke, Hinata and Itachi.

As a conclusion this is a very good support/tank/runner unit for PVP, especially if you want to replace Gaara for someone who can tank a bit more damage and don´t mind having 1 point less than Gaara.